Electrophotographic material and process



United States Patent Claims. 0!. 96-1.5)

Electrophotography is a method of reproduction, under which electricalcharges and their changes influence the production of images. Theelectrophotographic material used for this purpose usually consists of aconductive or non-conductive support, on which is brought aphotooonductive layer which is over a conductive middle layer. Thephotoconductive layer is put into a state of hgh photosensibility bycharging itwith an electrostatic charge, for the purpose of performing areproduction. As soon as such electrophotographic material isphotoexposed under a pattern in a process of contact, a process ofprojection or an epidiascopic process, a latent electrostatic image ofcharge is obtained corresponding to the pattern. T h s charge image canbe rendered visible by manifold processes of developing, which are basedon the fact, that electrically charged preferably coloured materials areattracted by the charge remaining on the electrophotographic materialand are afterwards cause-d firmly to adhere by fixation. By use ofsuitable pulverized or liquid developers consisting of a mixture or adispersion of at least two components of different dielectric constants,it is possible to produce positive as well as negative reproductions ofan original.

The electrophotographic layer, when eleotrostatically charged and actingtogether with a support layer effecting the discharges determined thephotosensibility of the electrophotographic layer, and hithertogenerally consisted of a combination of a photoconductor and a binder ofinsulating qualities with a specific electrical resistance of about 10to l0 S2/cm.

In the production of electrophotographic layers it was assumed that thiskind of layer is rendered active only, if consisting of a photoconductorand binders of insulating qualities, the purpose of the latter being toprevent discharge in the unexposed areas.

As a rule the photo conductor is used in the binder in shape of a solidsolution or in a fine dispersion, resulting in a practically grainlessreproduction of the electrophotographic image.

Contrary to this the procedure, according to the invention, is basedupon the idea of producing photoconductors possessing per se bindingqualities and of applying them in the manufacture of electrophotographiclayers.

Compounds specified as photoconductors with proper binding qualitiescomprise, in one molecule, groups of the following kinds:

1) Groups determining electrophotographc efiiciency, i.e. so calledphotoconduction of the respective compound; t

(2) Groups, capable of reacting to such compounds showing sufficientadhering qualities with regard to the support of the photo conductinglayer which may consist of a metal plate, an aluminium plate or thelike.

The aforementioned groupings according to Nos. 1 and and 2 must bepresent in the same molecule designated above as photoconductors withproper binding qualities.

For the production of a photoconductor with proper binding qualities itis thus required to bring to reaction a photo conducting compound,possessing the qualities mentioned above under Nos. 1 and 2, with anorganic compound, guaranteeing after reaction the necessary sufir- "icecient power of adherence to the support of the conducting layer.

These photoconductors with proper binding'qualities are capable offorming per se, without addition of other binders, anelectrophotographic layer of a condition ranging from hard to flexiblewith good adhering qualities and with excellent electrophotographicefficiency. Such kind of photoconductors with proper binding qualitiesare produced, as already indicated, by the reaction of a photoconductivecompound with organic compounds forming after this reaction enlargedmolecules of resinous products having excellent adhesive qualities tometals, papers or artificial resins, eventually being simultaneouslycapable of forming films.

According to the invention, such photoconductors with proper bindingqualities before the forming of the electrophotographic layer aresupplied in form of resinous compounds, eventually separated fromby-products and afterwards Worked from their solution, dispersion orsmelting toward producing an electrophotographic layer. It hasespecially been found that epoxy compounds and organic isocyanatecompounds reacting with electrophoto graphically active compoundspossessing the qualities aforementioned under 1 and 2, under moleculeenlargement and by forming products of fair adhesive qualities,eventually by forming resinous products, in the reaction produce suchphotoconductors with proper binding qualities. Surprisingly, in thecourse of these changes, the organic eleotrophotographically activematerials (photoconductors) do not lose their electrophotographicefficiency.

It is known, that by the reaction of compounds hearing epoxyorisocyanate groups with components containing hydroxyor amino-groupingsartificial res ns of fair adhesive qualities powers may be obtained. Itwas in no way, however, to be supposed'that photoconductive compoundswhen bearing groups capable of reacting with compounds containingepoxyor isocyanate groupings, would not losetheir electrophotographicefiiciencies, when reacting with epoxyand/or isocyanate compounds,

It has to be considered in connection herewith that by the reactionmentioned new'groupings partly strongly and differently polarized arecreated, the infiuencesof which, with regard to the efii-ciency of thephotoconductor, were neither known nor presumable and that furthermorethere should originate from them sufiiciently adhesive materialsconstituting the electrophotographic layer. Furthermore, during thereaction mentioned a considerable enlargement of the molecules takesplace, because the isocyanate or epoxy compounds engaged in the reactionpossess per se a higher density and a complicated structure. I

According to the invention for, the production of proper adhesivephotoconductor-s of preferably organic compounds with a structureeleotrophotographically active is used a base compound, containing,besides, groups capable of reacting with isocyanate of epoxy groupsunder enlargement of the molecules. Compounds of .the kind mentionedare'brough't to reaction with epoxy compounds or isocyanates Groups ofthese compounds capable of reacting in the sense of the invention aree.g. H,

, NH NHR, -NH',' COOH,, 'CONH CONHR,' SO H, SO NH SO NHR, OH, SH capableof reactions wherewith R may designate an possibly substituted isocyclicor heterocyclic ring system.

For the production of photoconductors with appropriate bindingqualities, the photoconductors, e.g. of the classes of compounds givenin the following, can be caused to react with epoxy resins orisocyanates, if they contain the aforesaid groups capable of reactionwith epoxides or organic isocyanates, possibly besides othersubstitutents not capable of reaction.

photo As suitable classes of compounds there are given by way ofexample:

1,3,4-oxdiazol compounds according to the German Patent 1,058,836,multinuclear cyclic hydrocarbons according to German Patent 1,060,2591,3,4-triazol compounds according to German Patent 1,060,260,azomethines according to German Patent 1,060,712,4,5-diphenyl-imidazolone or 4,5-diphenyl-imide-azole-thio-(2)- compoundsaccording to German Patent 1,060,713, pyrazoline compounds according toGerman Patent 1,060,714, acyl-hydrazones according to German Patent1,101,145, anthracene compounds according to German Patent 1,102,556,compounds according to German Patent 1,105,- 713, aryl-furanes,aryl-thiophenes and aryl-pyrroles according to German Patent 1,105,714,1,2,4-triazine com-- pounds according to German patent applicationpublished under number 1,099,846,l,2,5,6-tetra-azo-cyclo-octateracene-(2,4,6,8)compounds according toGerman Patent 1,110,007, keto-aniles, thiazole compounds; aromatic orheterocyclic ketones or thioketones, organic metal complex compounds,acridine dyestuffs according to the dates and definitions given bySchultz, Farbstofitabellen, vol. 1, 7th edition (1931), pages 383-390,chinoline dyestuffs according to dates and definitions given by Schultz,Farbstofftabellen, vol. 1, 7th edition (1931) pages 391-398, azinedyestuffs according to dates and definitions given by Schultz,Farbstofftabellen, vol. 1, 7th edition (1931), pages 407-429, oxazinecompounds and dyestuffs according to Schultz, Farbsto-lftabellen, vol.1, 7th edition (1931), pages 430-447, flavone compounds such as morine,quercitrine, etc. These dyestuffs shall not contain any -SO groups notcapable of reaction and shall not be present inform of salts.

As reaction compounds containing epoxy or isocyanate groups for theproduction of properly adhesive photoconductors, compounds of theseclasses already known or newly to be created may be chosen, if theycontain one epoxy and/or isocyanate group at least per molecule and iftheir structure is of such a kind, that they render adhesive qualitiesor are able to form films after reaction with the system communicatingelectrophotographic efficiency. For the supply of bidimensionalcondensated photoconductors, electrophotographically active substanceswith two groups capable of reaction may be taken as a base on one hand,brought to reaction with compounds having at most two epoxy orisocyanate groups. Proper-1y, adhesive photoconductors of resinousstructure on the other hand may be obtained by bringing to reactionelectrophotographically active materials, showing at least one groupmentcapable of reaction with an epoxy or isocyanate compound, having atleast two'of these groups per molecule.

It is furthermore possible to change the photoconductors according tothe invention to such an extent as to adapt them to spec-ialrequirements, be it by introduction of most different chemicalcompounds, having one or several epoxy and/ or one or several isocyanategroups and which, besides, are of different chemical structures be it byfurther partial reaction not only with photoconductors but also withother materials not electrophotographically efficient and effecting,e.g. a cross-linking, the materials according to the invention withregard to their qualities of electrophotographic efficiency, ofsolubility, adhesion as well as in their mechanical dates, e.g.resilience, eveness and resistance of surface, resistance against othermaterials etc.

As reaction components containing isocyanate groups those are of valuehaving one or several isocyanate groups e.g. attached to the aromaticring system, or furthermore those to be brought to partial reaction withaliphatic and/or aromatic monoor poly-amines and/or monoor poly-alcoholsand/or monoor poly-carbonic acids. Prototypes of these compounds aretoluylene-2,4-(2,6)- di-isocyanate, tri-phenyl-methane-4,4,4"-tri-isocyanate, naphtalene-1,5-di-isocyanate, di-merized isocyanates,f.i. formed from 2 mols of toluylene-2,4-di-isocyanate or productsresulting from the partial reaction of 1 mol of 3-tri-hydroxy-methylenepropane with 3 mols of toluylene 2,4-di-isocyanate. Another choice withregard to the structure of the isocyanates and their further change tocomponents of reaction containing free isocyanate groups is given by G.Schulz, Die Kunststoffe, Munich, Carl Hanser, Verlag, 1959, pages243-251.

As reaction components containing epoxy groups, several classes areknown. The reaction per se of photoconductors fit for this purpose withsimple epoxides, as ethylene or propylene oxide, results in wax-likecompounds, when polycondensation occurs. For special uses, however,those are of value, deriving from the type of phenyl-glycide-ether,ethyl-glycide-ether, and di-glycideether of the5,fi-bis(4-oxy-phenyl)propane with epichlorohydrin, while their epoxygroups are conserved, eventually also their higher molecular products ofreaction, containing several of the groups set into brackets in thefollowing formula:

R meaning an aliphatic radical and H. Epoxides, however, also of longerchains, linear or branched aliphatic structure containing one or severalepoxy groups are of value, whereby reaction production from2,3-epoxy-propanol-(1)-allyl-ether may be supplied with furtherreticular qualities in the electrophotographic layer, according to thetype of drying oils, eventually by a siccative process. Suited are,furthermore, epoxy esters of aliphatic or aromatic monoor poly-carbonicacids of the general structures. i

wherewith R can mean an aliphatic or aromatic group.

A choice with the execption of the epoxy esters is given by G. Schulz,Die Kunststolfe, 1959, pages 240-243.

As already outlined, for the purpose of adaption of properly adhesivephotoconductors with regard to their possibility of use isocyanate orepoxy groups, not having reacted during the reaction with the groupssupplying electro-photographic qualities, can be brought to reaction forthe purpose of further reaction with materials, reacting with epoxy orisocyanate groups. Such reaction components are e. g. alcohols,preferably of longer chained structures or of those containing severalhydroxyle groups, but also unsaturated alcohols, wherewith the latterare inclined toward reticular structure, eventually if submitted to asiccative process.

But also monoor poly-amines, as e.g. amines or acidamides, obtained fromC2'C20-fat-aCidS are useful. Suited are also such kinds of organiccompounds, containing one or several free carboxyl groups as e.g.phthalic acid, terephthalic acid, tri-mesine acid, adipine-, suberic-,azeleinor sebacine-acid, unsaturated di-carbonic acids as malein-,fumaric acid, citric acid, fat acids, oxyor ketofat acids orpolyunsaturated acids, as linseed oil-, fishor train oil-acids,permitting a subsequent hardening accordreaction, as e.g. proteins ortheir products of decomposition, as amino acids, cellulose,cellulose-ether or -ester, acetals or esters of the polyvinyl alcoholwith hydroxyl groups capable of reaction and the like.

Furthermore, the additional components of reaction can be formed in sucha way that they possess substituents reacting with different speed withepoxy or isocyanate groups. Suited are e.g. for a partial reactionsuch-compounds bearing a hydroxyl-, sulfhydryL, carboxyl oracidamide-group and additionally an aminoor iminogroup. In such a waylonger chained aliphatic w-amino alcohols as well as amino-phenolsor-naphthols, react at low temperatures of reaction already practicallycompletely with their aminoor imino-group together with epoxidesor'isocyanates forming properly adhesive photoconductors dissolving insolvents.

This photoconductor after production of theelectrophotographic layer byway of heightened temperature of reaction or by catalysts, per exampleby burning .in at 130-.160 C. can be brought to reaction e.g. with thehydroxyl group." As a product of reaction, an electrophotographic layeris. obtained, no more'solub'le or under difficulties only, under'a threedimensional reticulation of the oxy or isocyanate groups, still presentin the molecule, but not having been caused to react.

A further possibility of variation consists in that the groupingsrendering electrophotographic activity possesses two or more groups permolecule reacting with different speed of reaction with isocyanates orepoxides, and that it reacts with one of it, that is, with an epoxy, andwith the other one which is different from the first component ofreaction containing epoxy or/and isocyanate groups.

The electrophotographic layers, produced according to the procedures ofthe invention obtained under application of properly adhesivephotoconductors, evidently contrast with usual present practiceaccording to which photoelectric layers must consist of a solid solutionor dispersion of a photoconductor in a binder possessing insulatingqualities.

The proper adhesive photoconductors formed, accord ing to the invention,have the advantage compared with the solid solutions of photoconductorsin a binder of insulating qualities, that the materials according to theinvention do not tend towards cristallization, that in organic solventsphotoconductors difficult to dissolve are rendered easier solublethat'no cristallization or separation of the photoconductor can takeplace, when the limits of compatibility are passed can ensue from theelectrophotographic layer and that the difficulties regarding theirpermitting to be combined with binders of insulating qualities, alsowith regard to the choice of the solvents applicable will not arise,furthermore, that the rate of the groupments causing the photographiceffect to those causing adhesion is constant and also remains constantduring the process, while the solvent is evaporated. A further advantageof the procedure according to the invention is to be seen in that thatthe electrophotographically active groups possess a spacious definedarrangement in the photographic layer, that they are present in amolecular distribution and that they do not tend toward the formation ofagglomerations of the photoconductor as it is the case with binders ofinsulating qualities. The materials according to the invention thereforealso render more homogeneous and uniform electrophotographic layers.

For the production of properly adhesive photoconductors, according tothe invention, electrophotographically active materials are brought toreaction with isocyanate and/or epoxides groups containing compounds,

eventually under simultaneous or subsequent addition of furthermaterials capable of reaction with epoxides and/ or isocyanates whichare not photoconductors, preferably in solvents eventually under raisingof temperature and/or under presence of catalysts.

' The forms of this procedure by which the produced properly adhesivephoto conductor during the reaction in precipitated from the solvent,while the original products remain soluble are especially valuable forthe separation of the same.

The photoconductors properly adhesive can serve per se, that is, withoutthe addition of binders for the production of the electrophotographiclayer. For the shifting of the spectral sensitivity of the layerproduced usual sensitizing dyes can be added to the same.

The electrophotographic material, also called electrophotographic plate,without limiting its application to plate shaped products, usuallycomprises of a support material either conducting electronics and ionsor electrically 3 non conducting. For electrically conducting material,f.i.

are considered metals in form of plate shaped objects, as also surfacesrendered rough by a galvanic or mechanical procedure eloxated,phosphorized, electrically conducting papers, fleeces, tissues or foils.

' Especially valuable are such flat surfaced objects, as papers, fleecesor foils, rendered conducting by being coated with a thin metallic layerin the vacuum. If a non conducting support is used it is advisable, inorder to increase the capacity of conduction between theelectrophotographic layer and the support to use an auxiliary interspacelayer which increases and holds constant the electrical capacity ofconduction.

It is furthermore necessary if support materials of absorptivecapacities are applied to provide these with a covering auxiliary layer,favoring the formation of the electrophotographic layer in uniformcondition and equal thickness. For the production of such auxiliarylayers increasing the conductive capacities or serving as a cover theremay be used, for example, organic colloids, as gum arabic polyvinylalcohol, partial acetals of the vinyl alco hol, gelatine, agar-agar,carragheen, polyuronic acids or their salts, water solublecellulose-ether and -esters, as methyl cellulose or alkali salts of thecellulose glycol acid, as well as of the polyacrylates or methacrylates,acrylacid-amides, starch, starch-ether, starches discomposed asdextrines or roasted starches, per se or in combination with mediumsholding them in a humid state, as for example glycerine sorbite,polyglycolene, polyglycol ethers as well as with salts as f.i. zincchloride, calcium chloride, ammonium chloride, ammonium nitrate, etc.,as well as also in connection with polyalcohols, boric acid etc. Forspecial methods of application it is necessary in order to increase thestability of the capacity of charge of the electrophotographic plate toarrange an electrical interspace barrier layer between theelectrophotographic layer and the support, permitting the flow ofdischarge in one direction only. Suitable for this purpose areespecially oxides of copper, cadmium, as well as of aluminum.

The properly adhesive photo conductor rendering the electrophotographiclayer is spread upon this support material prepared in such a manner.

The electrophotographic layer can be produced by dissolving the properlyadhering photoconductor e.g. in a solvent or bringing it to a finedispersion in a solvent or in water and to spread this preparation byway of spreading means, e.g. centrifugation, wash-up rolls, or scrapingmeans, as with rakes or air brushes, with pressure rolls, transfer ordistributing rolls, by dipping or electrostatic spraying. For specialforms of application it can however, be suitable superficially to embedthe properly adhesive photoconductor in a melted condition in a supportmaterial in a very thin layer. Furthermore, the properly adhesivephotoconductors can be spread in a melted condition onto the supportmaterial, wherewith one can make use of the liquid state of thephoto-guiding mal terial eventually caused by higher temperatures orhigh pressure in extruders or press means, preferably in such onespermitting a calibration for obtainng uniform thickness of the layer.

The production of image .by way of the electrophotographic materialusing properly adhesive photoconductors according to the invention canensue in the known manner just the same as with otherelectrophotographic materials. For this purpose the electrophotographicmaterial is for instance charged with a coronar discharge of 3-8 kv.negatively or positively or an electrical potential is communicated toit by contact or frictional electricity. Afterwards theelectrophotographic material is photo-exposed. At the spots influencedby the light, the electrical potential is diminished or eliminated. Theremaining residue charges, arranged in the shape of the pictures to bereproduced are rendered visible by way of known developing systems, suchas toners of artificial materials, dyestuffs and/or soots, as well asglass pearls or metal powder. Likewise the rendering visible of thelatent electrophotographic image is effectuated with liquid developerswherewith the liquid phase of the developer must have a smallerelectrical capacity of conduction and a dielectric constant differentfrom the one of the matter dispersed in it and used for the creation ofthe image and for the rendering adhesive, which are preferably dyed.

The image rendered visible by this developing is fixed according toknown procedures as for instance, by smelting it or by the effect of thetoner causing the solvents to swell.

The electrophotographic material developed but not yet fixed isfurthermore suitable for the production of transfer copies, by way oftransferring the toner of the developed electrophotographic image byelectrostatic means onto other support materials, as for instance,ordinary paper, foils or metal plates.

The electrophotographic material, according to the invention, permits arepeated reproduction of the image on the same plate, by bringing ontothe same plate after the fixation of an electrophotographic picturepreviously created further images and onto the image already cre ated,wherewith these images can be created in several and different colours.The material, according to the invention, is furthermore suitable forcontinued creation of images, especially if the image created isrendered Onto other materials by way of a transfer procedure. With thisform of application an interim cleaning is necessary of theelectrophotographic material of adhering toner residues, as well aseventually the complete discharge before the new creation of image. Itis herewith possible, to produce a greater number of differentreproductions with one and the same electrophotographic plate, Wherewiththe continued procedure of transfer can be rendered consecutive andautomatic. It is further-more possible, to remove the developedelectrophotographical image by wiping it off and without a renewedcharging and photo exposure, by effect of the developer system alone, tohave the image newly reappear. Herewith the contrast increases, as thesurface-bound residue charges, serving the image compilation, wereremoved. This method permits corrections to be made also with regard tothe quantities of the toner to be applied. Preferably a dimly lightedroom is used for the Work.

A further form of application of the electrophotographic layer suppliedaccording to the invention under application of properly adhesivephotoconductors consists in the production of printing plates,especially for the offset printing process.

Herewith a conducting support material, consisting of metal plates ormetal foils also such ones having been roughed up by mechanical orgalvanic means to a surface condition of finest grain structure, or ofconducting paers, foils or fleeces eventually after covering it with acolloidal layer having it coated with the electrophotographical layer.If using metal foils with grain structure or of aluminum plates with aporous hydrophilic surface produced by oxidizing or phosphatizing theproduction of pressure plates succeeds also without the intermittance ofa printing dye repellent hydrophilic colloidal layer. None conductingsupport materials can, however, also be used, if the colloidal layer isrendered electrically conducting. For the production of the colloidallayer gelatine, polyvinyl alcohol, alginates, salts of the acryl ormethacryl acids, acryl-acid amides, cellulose-ether or -esters swellingin water, zinc salts of the resinous acids or polyurone acids etc. areusable. For this form of application the properly adhesivephotoconductor is created in a form still dissolvable in solvents and athreedimensional reticulation is avoided.

The printing plates produced according to the procedure of the inventionare electrostatically charged in known ways and photo-exposed under apattern or in the procedure of projection. By developing with a toner,capable of absorbing fat printing dyes and being insoluble in solvents,permitting to dissolve the electrophotographic layer, theelectrophotographic image is created. The same is fixed by solventscausing the toner to swell or by heating up to about C. Afterwards byoverwiping or by bathing in a mixture of solvents theelectrophotographic layer is dissolved while the image created by thetoner remains. The colloidal layer situated beneath theelectrophotographic layer of the hydrophilic support adequate forprinting purposes is laid bare. With the application of aluminum or zincplates the printing plate is rendered ready for use by wiping over itwith a 30% phosphoric acid and afterwards by rendering it humid,eventually under addition of moistening means, the printing dye suitablefor offset printing processes is brought onto it. Printing plates ofthis kind permit high numbered edition under exact printing procedures.

The following represent special realized forms of the invention withoutlimiting the object of the invention to them:

EXAMPLE 1 The example relates to the production of a photoconductorproperly adhesive, the electrophotographically active grouping of whichis derived from the class of the thiazoles, the free amino group ofwhich is brought to reaction with a modified isocyanate containing threefree isocyanate groups per molecule.

50 g. of 2 (4 aminophenyl) 6 methylbenzthiazole,

fusing point=l92 C., are dissolved under reflux boiling in 750 cm. ofwater free cyclohexanone, the solution is filtered hot.

87.5 g. of the modified tri-isocyanate (commercial product produced byFarbenfabriken Bayer AG. and sold under the trademark Desm odur L), 75weightapercent in ethylacetate are added to it and brought to reactionfor 30 minutes after removal of the ethyl acetate under reflux boilingat a temperature of C. The solution is left standing overnight, Whilethe reaction product is flocked out. The precipitation is filtered,boiled up with 500 cm. of acetone, whereby small parts of2-(4'-aminophenyl)-6-methylbenzthiazole having not reacted, aredissolved. Separated from the insoluble product of reaction byfiltration in a hot state, washed several times with cold acetone on thesuction filter and dried by 100 C., a product of addition is obtainedsoftening between 220-225 C. and afterwards congealing to a hyalinestate. This product of reaction dissolves in cyclohexanone,dimethylformamide, methylcyclohexanone, for-mamide, tetrahydrofurane andhardly dissolves in hot fbenzole. The compound practically colorless isalready usable in this form as a properly adhesive photoconductor.

9 For the. production of the electrophotographic layer 100 g. of thebefore mentioned properly adhesive photoconductor is dissolved in 500g.of cyclohexanone and 200 g. of methyl-ethyl-ketone and a layer is spreadonto a surface cleansed aluminum plate by way of a centrifuge, that athickness of layer is obtained of 0.005 mm. in dry state. Afterexpulsion of the solvent by heating the plate up to 120-130 C. in an aircurrent, followed by a cooling down to room temperature the'electrophoto-graphic plate is ready for use. It consists of an evensurface of high gloss, together with a considerable hardness of surface.

Electrophotographic plates spotted by fat or toners can easily becleansed by washing with water and washers, without losing theirefiiciency'. For this purpose the electrophotographic plate is rubbedwith a moist cotton pad, rinsed with distilled water and-dried in a warmair current. The plate can immediately be used again.

The electrophotographic plate thus produced is charged for a short timeunder an arrangement of spray electrodes with 6-7 kv., photo-exposedunder a pattern with a cold light UV valve for 3-16 seconds andafterwards powdered with a mixture, consisting of the toner and smallglass pearls, the toner consisting of piccolastic resin, soot and blackdyestuffs. On a support of metallic g-loss an image rich in contrasts isproduced possessing a large spectral dispersion, which can be firmlyfixed by heating up to 120 C. and by the reaction of the vapors of thesolvents attacking the developing powder. The electrophotographic-platehas a high sensibility already'in the long wave ultraviolet spectralregion. In the light of an electric bulb, 'as well as in. diffuse daylight, its sensitivity is so small that the production of the picturecan be carried through in a moderately blacked out room by full electricbulb light.

EXAMPLE 2 The example relates to the production of a properly adhesivephotoconductor, the electrophotographically active groupings derivedfrom the class of the thiazoles and which possesses a free amino groupfor the further reac tion with isocyanates. This electrophotographicallyactive group is brought to reaction in such a way with a modifiedisocyanate with three free isocyanate groups per molecule, that smallparts of free isocyanate groups are sustained for the realization ofreticulating reactions.

40 g. of 2-(4-aminophenyl)-6-methylbenzthiazole, fusing point=192 C.,are dissolved under reflux boiling in 750 cm. of water freecyclohexanone; the solution is filtered in a hot state;

90 g. of the modified tri-isocyanate (commercial product produced byFarbenfabriken Bayer A.G. and sold under the trademark Desmodur L), 75weight-percent in ethylacetate are added and brought to reaction afterremoval of the ethyl-acetate for 30 minutes under reflux boiling at atemperature of 155 C. The solution is then cooled down to roomtemperature and is left to itself overnight, while the photoconductorflocks out. It is separated by filtration. In

500 cm. of acetone afterwards suspended and suctionfiltered, the filterresidue is washed several times with cold acetone.

80 g.'of the reaction product still somewhat moistby acetone aredissolved in 250 cm. of cyclohexanone and 20 cm. of ethyl-glycol addedto it and left to react during 20 minutes at a temperature of 125 C. Theproperly adhesive photoconductor is dissolvable in cyclohexanone. Thereaction product obtained is thinned down with 100 cm. offmethylethylketone and heated up to 60 C.,

usedfor the covering layer of a cleansed aluminum plate inacentrifuge.vThe plate covered with said layer is dried in a warm air current andafterwards burnt in a drying chamber or by way of an ultrared radiatorfor 30 minutes at a temperature of 130140 C. Its thickness of layer is0.006 mm. An electrophotographic layer is obtained especially resistingagainst scratches and practically insoluble in solvents, which layer isused for the production of images according to Example 1. It is of thesame water and washer resistance qualities as the electrophotographicalplate mentioned in Example 1.

Transfer The electrophotographic plate is negatively charged with 7 kv.photo-exposed for 10 seconds under a pattern to cold light UV-valves anddeveloped with the commercial product sold under the trademarkGraph-o-Fax- Toner. charged with 1 kv. A sheet of common writing paperis laid upon the powder image not yet fixed and brought together'withthe plate into the electric field of a tension of 7 kv., in such a way,that the negative arrangement of electrodes is situated behind the backcover of the paper. By transfer on the writing paper there is obtainedfrom the reverse side powder image an original of high contrast andclearly readable. The image transferred is fixed by heating up to 110 C.

EXAMPLE 3 This example relates to the production of a properly adhesivephotoconductor, the electrophotographically active groups which derivefrom the class of thiazoles and which possess an amino group capable offurther reaction with isocyanates.

In the first stage of reaction it proceeds that a considerable surpluspart of free isocyanate groups is sustained after the reaction with thethiazole compound, which may then be brought to reaction with a fatalcohol in order to increase resilience.

455 g. of 2-(4-aminophenyl)-6-methylbenzthiazole, fasing paint 192 C.,are dissolved in 400 cm. of cyclohexanone at 60 C. and added to it are175 g. of the modified tri-isocyanate (commercial product produced byFarbenfabriken Bayer A.G. and sold under the trademark Desmodur L) andafter the removal of the ethylacetate at C. heated up during 7 minutesuntil the cyclohexanone begins to boil. To this solution are added inone gulp 40 g. of an n-C -fat alcohol (commercial product sold under thetrademark Lorol C during 15 minutes a heating up to 150 C. ensues andthen cooling down is permitted. The reacting solution remains clearafter having cooled to room temperature. It is of a high viscosity andmay be thinned down with acetone or chloroform without a precipitationensuing.

For separation the properly adhesive photoconductor is precipitated fromthe reacting solution by pouring it into 2 litres of benzene (boilingrange -140 C.), the properly adhesive photoconductor being obtainedafter several decantations-and comminutions in benzine and after dryingat 100 C. in a vacuum drying chamber as a whitegrey powder.

For the production of the electrophotographic layer. 50 g. of theproperly adhesive photoconductor produced as described above isdispersed in cm. cyclohexanone and dissolved by heating up to 100 C. Thesolution is then cooled and 200 cm. of acetone are added to it. Thesolution formed remains durable at room temperature. There is no C -fatalcohol odor.

A cleansed aluminum plate is so covered with a layer in the centrifuge,that a thickness of layer of 0.004 mm. in dry state is obtained. Afterspreading of this preparation it is dried in a warm air current andafterwards heated up for the expulsion of cyclohexanone residues to Theelectrophotographic plate is now positively 100 C. in the air current.The surface of the electrophotographic layer is adhesive and elastic atthis temperature. If cooling down to room temperature is effectuated anelectrophotographic layer of high gloss, suflicient hardness and greatresilience is forming.

It is dissolvable in a mixture of 2 parts of ethanol and 1 part ofacetone and can be used for the production of printing plates. Thiselectrophotographical plate may also be cleansed with water and washersfrom adhesive toner materials and fat traces, as e.g. finger prints,with out causing loss of the electrophotographic efficiency afterdrying.

EXAMPLE 4 g. of (4-hydroxybenzylidene)-4'-N-di-ethylaminoaniline in 250g. of cyclohexanone. Small parts not dissolved are removed by filtrationand in the solution are added under stirring 44 g. of the modifiedtri-isocyanate (commercial-product produced and sold by FarbenindustrieBayer AG. under the trademark Desmodur L), 75 weight-percent in ethylacetate and after expulsion of the ethyl acetate brought to reaction for40 minutes at 120 C.

The reaction product, spread onto a glass plate, congeals to a yellowcolored resinous product with good adhesability on the support layer.

100 cm. of the reaction solution obtained, durable in cool state, arethinned down with 300 cm. of methyl-ethyl-ketone; this solution beingthen by way of a centrifuge spread in such a manner on an aluminum plateof high gloss, which has been carefully cleansed, that a thickness oflayer of about 0.006 mm.

is uniformly forming.

This electrophotographic layer is of gold yellow colour and is highlyphoto-sensible as well in strong bulb light as in the ultravioletspectral region.

Charged according to Examples 1-3 and photo-exposed during 1-3 secondsto cold light UV-valves, an electrophotographic image rich in contrastsis obtained after developing with the toner sold under the trademarkGrapho-Fax, well known as a commercial product, in combination withglass pearls. This image is fixed by help of warmth. Thiselectrophotographic plate is furthermore adequate for the image transferaccording to Example 2.

EXAMPLE 5 On a transparent paper of 60 g./m. weight, a preparationadequate for the production of a conductive interspace layer consistingof g. of polyvinyl alcohol, of medium molecular weight 10 g. ofpolyethylene-glycol-ether,

10 g. of sodium chloride, and 930 cm. of Water is spread with a wash uproll and scraped by way of an air rake, so that a layer of a thicknessuniform of 8 g./m. in dry state is formed.

The auxiliary layer being dried down to a humidity rate of 1218% in awarm air current after the spreading,

is coated on a centrifuge, with a scrape solution, used for theproduction of the electrophotographic layer according to Example 3, insuch a way that an electrophotographic layer of a thickness of 0.006 mm.is obtained. After drying of the electrophotographic layer subsequentclimate conditioning at a relative 65% air humidity at 20 C. theelectrophotographic material is ready for use.

The transparent and practically colorless material is renderedphoto-sensitive by help of a 8 kv. arrangement of spray electrodes,consisting of tungsten wires commonly used in the electric bulbmanufacturing the material being charged with an intermediate space of15 mm. and a distance of 15-20 mm. from the positive electrode formed asa support layer, in such a way that the electrophotographic layer islaid by the negative electrodes.

Photo-exposed under a pattern to UV-cold light valves during 20 secondsand afterwards developed by a developing system, consisting of thecommercial toner sold under the trademark Graph-o-Fax, a commercialproduct, and glass pearls as well visible reproduction is obtainedsuitable on account of its transparence as an intermediate originalafter its being fixed by trichloroethylene vapours.

Unfixed the developed electrophotographic material is usable for thetransfer of images.

EXAMPLE 6 The example refers to the reaction of a photoconductor of thethiazole class with an epoxy compound of the di-2,3-epoxy-propane-ethergroup of the bis-fifi-( l hy droxyphenyl propane. i

The mixture of reaction is condensated for 60 minutes at 154 C. andafterwards cooled down to 40 C.

To this product of reaction are added: 450 g. of methylethyl-ketone;this preparation is used for the production of the electrophotographiclayer.

This coating of an aluminum plate of high gloss and ofa thickness ofO.1O.3 mm. is effectuated, by spreading the solution committing theelectrophotographic layer with a centrifuge in such a way on to thesurface, that a layer of a thickness of about 0.006 mm. in dry state isobtained The electrophotographic layer is slightly surface dried in awarm air current and submitted to an aftertreatment during 30 minutes atC. for the expulsion of solvent residues. After cooling theelectrophotographic layer congeals and is ready for use. It renders awell readable reproduction of a pattern of high contrasts after beingcharged up to 6 kv., photo-exposed to UV-cold valves for 15 seconds anddeveloped according to Examples 1 to 5; the image can afterwards hefixed by heating up to 110 C.

EXAMPLE 7 This example describes the use of a support material ofinsulating qualities, on which it is possible, to create anelectrophotographic image by help of organic properly adhesivephotoconductors although no discharge of electronics essential can takeplace on account of the insulating qualities of the support.

For this purpose a plate of window glass of the thickness of about 2 mm.is coated by help of a centrifuge with a properly adhesivephotoconductor described under Example 4, in such a Way that thethickness of the electrophotographic layer is about 0.03 mm. Theelectrophotographic layer is superificially dried on the centrifuge withan ultra red radiator and afterwards burnt in for 10minutes at about C.The electrophotographic'layer 13 thus formed has excellent adhesivepowers to glass and besides a great hardness and a considerableresistance against grinding wear. This electrophotographical layer isdissolved by higher ketones, cyclohexanone and dimethylformamide. i

This electrophotographic plate produced by making a glass plate servesas support and is charged up under an arrangement of spray electrodes of7 kv. for 10 seconds, in such a way that the tungsten wires serving asnegative electrodes are confronted to the electrophotographic layer witha distance of 13 mm., while the glass support is laid upon the positiveelectrode. The electrophotographic plate charged and thus made photosensitive is photo exposed for seconds under a pattern to UV-cold lightvalves and after developed with a developing system, consisting of glasspearls and the direct toner sold under the trademark Graph-o-Fax. Anelectrophotographic image of high contrasts is produced on a transparentsupport which image after being fixed by heating up to 120 C. or bysolvent vapours can firmly be fixed onto the electrophotographic layer.This electrophotographic plate is suited for repeated production ofelectrophotographical images and can be used for the production offurther copies by help of other methods of reproduction.

The following Examples 8, 9, 10 and 11 describe properly adheringphotoconductors, the electrophotographically active groupings of whichoriginate form the photoconductive ket-to-aniles, which groupings bearthe substituents, capable of reacting with epoxide or isocyanategroupings.

EXAMPLE 8 N(4-ethyl-(B-oxyethyl)-aminophenyl-rnethylene) 3'-nitro-aniline of subsequent formula was produced by reaction ofbenzoyl-3-nitro-aniline with N-ethyl- (B-acet-oxyethyl -aniline withphosphoroxy-chloride at 120 C. and subsequent saponification of theacetyl group.

The isocyanate component, containing about two free isocyanate groupsper molecule which component communicates adhesion and is used for theproduction of proper-adhesive photoconductors, is produced in thefollowing way:

32 g. of 2-ethyl-2-butyl-propandiol-l,3 (corresponding to 2 mols) aredissolved in 100 g. of cyclohexanone and then dissolved in 70 g. oftol-uylene-2,4-diisocyanate (it is also possible to use 70 g. oftoluylene-2,6-diisocyanate or 70 g. of a mixture of both of thecompounds) 200 g. of cyclohexanone are added.

50 g. of modified isocyanates, described above are dissolved in g. ofcyclohexanone. Added are methylene)-3-nitro-aniline, dissolved in '200g. of cyclohexanone, and the mixture is brought to Herewith an aluminiumplate submitted to a galvanic pre-treatment is coated in such a way,that a thickness of layer of 0.0060.02 mm. in dry state is formed. Afterdrying at C. in an air current an electrophotographic layer welladhesin-g to metals and scratch-resistant results, fit for being usedaccording to the preceding examples after negative or positive chargingfor the reproduction of images and eventually for their transfer.

EXAMPLE 9 30 g. of 4-di-methyl-amino phenyl-phenylmethylene)-3'-oxy-aniline of the subsequent formula CH OH are dissolved in warmcondition in 100 g. of cyclohexanone. To this solution are added 27.7 g.of the modified isocyanate with three isocyanate groups per molecule(commercial product produce-d and sold by Fa-rbensindustrie Bayer A.G.under the trademark Desmodur L) 75 weight percent in ethyl acetate,thinned down with 50 g. of cyclohexanone, and after expulsion of theethylacetate condensated for 1 hour at 148 C.

The reaction product by this reaction has suffereda considerableincrease of viscosity no longer permits three dimensional reticulationwith diisopropylene-triarnine.,

The solution is of green color.

15 g. of above condensated solution are thinned down with 25 g. of:methyl-ethyl-ketone,

15 g. of cyclohexanone, and

15 g. of buty-l-acetate and for the coating of a copper foil cleansed atits surface, of a thickness of 0.01 cm. by washing up and scraping witha rake from roll to roll coated and afterwards burnt in for a short timewith ultrared radiators at 150 C. and then cooled.

The electrophotographic layer originating from the proper adhesiveprotoconductor, has a thickness of about 0.004 m m.; it is of highphotosensibility already in the long wave UV-region and produces imagesrich in contrasts fit for transfer of images, f.i. onto writing paper.The electrophotographic layer moderately dissolves in ethanole,wherewith the toner image burnt in, the latter containing polystyrol orother artificial resins undissolvable in alcohols, firmly adheringremains on the surface, while the said layer is at once dissolvable byketones and esters. It is therefore especially adapted for theproduction of printing plates. The electrophotographic layer firmlyadheres to metals and has a good resilience at high scratch-resistance.t

The electrophotographic material described above is excellently suitedfor the image transfer. For this purpose it is treated with atribo-electric powder, consisting of a toner and glass pearls or ironpowder, and the ensuing electrophotographic image is not fixed.Afterwards the electrophotographic plate is caused closely to contact atransfer sheet consisting of paper, of paper soaked in artificialresins, or artificial materials, and thus introduced into a sufiicientlystrong electric field, the electrode of which charged up differently tothe toner charge is arranged toward the reverse of the transfer sheet.The electrophotograpric image transferred is then fixed by heating up orby solvent vapours, eventually under simultaneous heating.

A special sample concerns the production of an offset printing plate,for which a toner suited for printing purposes is transferred from theelectrophotographic layer onto a commonly used printing plate, as usedfor fiat printing submitted to a special treatment for offset printingon which plate it is firmly fixed. This printing plate is suited for theproduction of flatprinting.

EXAMPLE 10 170 g. N-(4-di-methyl-amino-phenyl)-phenyl-methylene2'-methyl-4-nitro-5-butyl-.amino-aniline of subsequent formula, fusingpoint f=l03 C.

Dried at 130 C. a hard but resilient electrophotographic layer adheringwell to the support material is produced, rendered photosensitive aftera negative or positive charging under an arrangement of spray electrodesof 5-8 kv. or by friction electricity, the region of photosensibilityranging from that of a mercury high pressure lamp to electric bulblight, reproductions rich in contrasts being obtained after development.

EXAMPLE II 65 g. ofN-(3-oxy-napthyl)-4-di-methyl-aminophenylmethyl-aniline of the followingformula:

CH3 CH3 produced by reaction of naphthol AS with dimethylaniline andphosphoroxy-chloride are dissolved in 250 cm. of cyclohexanone, asolution being added of 87.5 g. of the modified isocyanate with 3 freeisocyanate groups per molecule (commercial product produced and sold byFarbenindustrie Bayer A.G. under the trademark Desmodur L), 75Weight-percent of ethyl-acetate, dissolved in 16 200 cm. ofcyclohexanone, and condensated for 2 hours under reflux boiling.Subsequently 16 g. of a C -fat alcohol are added and reacted under afurther 30 minutes of reflux boiling. The photo conductor properlyadhesive of resinous qualities can be separated by precipitation withbenzine.

Examples 12, 13, 14 describe the reactions of photoconductors of theclasses of the eventually substituted aromatic or heterocyclic-ketonesor thio-ketones, both of the ring systems of which are connected by COor (IJS groups, containing further subst-ituents in the ring system orin the lateral chains, reacting with isocyanates and/or expoxidesforming proper adhering photoconductors.

EXAMPLE 12 31 g. of 2-(4-di-ethyl-amin0-2-oxy-benzoyl)-benzo-acid and0.3 g. of rhodamine B are dissolved in cm. of cyclohexanone. To thecooled solution are added 47 g. of the reaction product,containing'three free isocyanate groups per molecule produced from 1 molof l-tri-methylol-propane and 3 mol of toluylene-2,4- di-isocyanateand/or toluylene (e.g. a commercial product produced and sold byFanbenindustrie Bayer A.G. under the trademark Desmodur L) 75weightpercent in ethyl-acetate, dissolved in 100 cm. of cyclohexanone.

This mixture is condensated for 20 minutes at 151 C. under refluxboiling, a perceivable increase of viscosity ensuing. The product ofreaction is only limitedly compatible with acetone. If mixed withacetone at a rate of 10:1 the proper adhesive photoconductor isprecipitated. The reaction can be directed in such a way that across-linking does not yet take place.

25 g. of the reaction solvent are added to 25 cm. of methyl-ethyl-ketoneand 35 cm. of dioxane and after filtration they serve for the productionof the electrophotographic layer, an aluminum foil having achemical-galvanic gloss coat to it, being coated withit by help of acentrifuge, so that a layer thickness of 0.006 mm. in dry state isformed.

The plate coated is superficially dried on the centrifuge, by way of anultra red radiator, and then burnt in for 5 minutes at C. Anelectrophotographic layer glossy and mechanically firm adhering on thesupport as well as of a high grinding resistance is obtained. Thiselectrophotographi-c plate is charged electrostatically at -7 kv. for 3seconds and photo-exposed under a pattern for three seconds toUV-fluorescence valves and afterwards developed with glass pearls and adirect toner. An elec trophotographic image of high contrasts isobtained.

Another method of the reproduction of image consists in that the abovedescribed electrophotographic plate is photoexposed in charged conditionin a magnifying means, outfitted with a 150 watt-cinema-projection lampwith an opening rate of 1:5.6 at a distance of 30 cm. between objectiveand plate through a micro film. After development an electrophotographicimage rich in contrasts is here also obtained.

EXAMPLE 13 g. of 4-N-ethyl-(;8-oxy-ethyl)-amino-benzophenone 200 g. ofthe modified isocyanate (commercial product produced and sold byFarbenindustrie Bayer AG. under the trademark Desmodur L), 75weight-percent in ethyl-acetate, and at 100 C. condensated for so long atime (usually minutes), that the solution is still compatible withmethyl-ethyl-ketone and that no gelatination takes place.

100 cm. of the reacting solution are thinned down with 200 cm. ofmethyl-ethyl-ketone, and this solution is spread in uniform thickness oflayer of about 0.008 mm. onto an aluminum foil of high gloss.

The electrophotographic layer formed is dried at 120 C. in an aircurrent and then burnt in at 140 C. for a short time. Theelectrophotographic material formed after being charged with 7 kv. andbeing photo-exposed under a pattern to a mercury high pressure lamp oran impulse discharge valve after development produces reproductions richin contrasts.

EXAMPLE 14 For the production of the electrophotographic material thereis used as a support material a glass fibre fleece impregnated withartificial resins having an. even surface, on which latter it wasexposed to aluminum vapors. Onto this material there is spread in thecentrifuge a solution consisting of 50 cm. of the above-mentionedproduct of reaction thinned down with 100 cm. of methyl-ethyl-ketone and0.5 g. of brilliant green (according to Schultz, Farbstoiftabellen,1931, No. 760), the spread solution being superficially dried by ultrared radiators and being burnt in at 120 C.

A firmly adhesive electrophotogr-aphic layer of high grinding resistanceresults this layer according to the abovementioned examples being suitedfor the production of electrophotographic reproductions. Theelectrophotographic material has a serviceable photo-sensibility atelectric bulb light.

EXAMPLE 15 50 g. of 4-di-methyl-amino-phenyl-3'-oxy-naphthyl-2'- ketoneof subsequent formula:

are dissolved in 200 cm. of cyclohexanone. Added hereto are 104 g. ofthe isocyanate component described in Example 8, 52 weight-percent incyclohexanone, and condensation is effectuated at 135 C. for minutes.

50 cm. of the reaction product are thinned down with 50 cm. ofmethyl-ethyl-ketone and 50 cm! of ethyl-amyl-ketone and afterwardsfiltrated.

This solution is spread by help of a scrape machine outfitted withdosage rollers onto a cellulose paper exposed to aluminum vapors of 80g./m. weight, dried in a warm air current and then post-heated at 120 C.for a short time.

On account of the green color the proper adhesive photoconductor isphoto-sensitive. Negatively charged for 5 seconds with 7 kv. under acorona discharge with UV-cold light-valves and photo-exposed under apositive 18 pattern, after development with glass powder and a directtoner an image rich in contrasts is produced, fixed by heating or bysolvent vapors.

Another method of development generally applicable is the use ofso-called liquid developers consisting of a dispersion of dye particlesunder addition of soluble or dispersed artificial resins. In analogyherewith is the application of developers of powder condition withelectrophotographical layers derived from properly adhesivephotoconduotors.

This development can be carried through if the liquid phase of thedeveloper is thus formed that the electrophotographic layer is notdissolved. Preferably such electrophotographic layers are used,submitted to a postcondensa'tion after production.

The following Examples '16, 17 describe properly adhesivephotoconductors the electrophotographic classification of which isderived .from the class of acridine-dyestuifs, according to Schultz,Farbstofitabellen, vol. 1, Leipzig, 1931, pages 383390, as well asUllmanns Encyklop'aldie der Techn. Chemie, vol. 3, Munich-Berlin, 1953,.

pages 7l-72, which possess swbstituents, capable of reacting withepoxides or isocyanates and which have been caused to react withepoxideor isocyanate-containing compounds communicating an adhesiveeifect. Preferably salt-free acridine stuffs are used for the productionof properly adhesive photoconductors.

EXAMPLE 16 g. of the modified tri-isocyanate (commercial productproduced and sold by Farbenindustrie Bayer A.G. under the trademarkDesmodur L) are dissloved in 200 cm. of methyl-ethyl-ketone. Added to itis a solution consisting of 50' g. of2,7-di-amin-o-3,6-dimethyl-9-methyl-acridine (name of dye Euchrysine 2GNX), according to Formelbild 5 (structure) in Ullrnanns Encyklopadieder technischen Chemie, vol. 3, 1953, page 71, dissolved under refluxboiling in 200 cm. of acetone and 300 cm. of methyl-ethyl-ketone, andcondensated by further reflux :boiling for 10 minutes. Afterwards areadded 14 g. of n-butanol and a further reaction is carried on foranother 10 minutes as described above. The reacting solution containingthe proper adhesive photoconductor is thinned down with 200 cm. ofinethyl-glycol-a cetate and afterwards used for the coating layer ofmetal foil supplied with a galvanic oxide gloss, lined on paper.

The electrophotographic layer is dried at C. in a warm air current andafterwards submitted to a finish drying by a short time beating up withultrared radiators. This electrophotographic material is highlyphoto-sensitive in the spectral region ranging from violet to blue, asproduced by luminous matter-fluorescence lamps, used for photographictracing purposes. Further, it shows a high degree of photo-sensibilityin the spectral region of impulse discharge valves as used forphotographic purposes.

EXAMPLE 17 90 g. of the modified tri-isocyan-ate (commercial productproduced and sold by F-arbenindustrie Bayer AG. under the trademarkDesmodur L), 75 weight-percent in ethylene acetate, are added to 50 cm.of cyclohexanone and brought to reaction for '10 minutes at C.

24 g. of di-Z-ethyl-hexyl-amine having also been added.

71 g. of3-a-mino-6-di-methyl-amino-9-(4'-di-methylamino-phenyl)-acridin-e(Farbstotftabellen, vol. 1, 1931, No. 911), a free base, are dissolvedin a hot state in 700 cm. of cyclohexanone, filtered in hot conditionand used for the reaction together with the abovementioned reactingsolution for 20 minutes at about 150 C. This properly adhesivephotoconductor is excellently suited, on account of its increasedsolubility in ethanole or other commonly used solvents, for theproduction of an electrophotographic layer on such support materials,change-able after production of the electrophotographic image andsubsequent fixation of the toner by heating, into printing forms,preferably for offset printing process. For this purpose the preparationrendering the photosensitive layer is either spread onto a paperpattern, submitted to a preceding treatment according to U.S. patentspecifications Nos. 2,534,650, 2,681,617 or 2,559,610 or metal patternsare used for supports suitable for printing purposes, said patternspreferably of aluminum, being roughened to most fine grain conditioneither by galvanic or other means, their drying being effectuated atincreased temperature in an air current. After production of theelectrophotographic image under application of a toner suitable forprinting purposes, the plate fixed by heat is slightly wiped over withan alcohol moistened cotton pad not dissolving the electrophotographiclayer made to serve for the reproduction of the image. By a quick wipingover with phosphoric acid the printing plate is rendered ready for use.From a positive pattern a positive printing mould is obtained permittinga high numbered printing edition according to the offset process.

The following Examples 18 and 19 refer to properly adheringphotoconductors, the electrophotographically active groupings of whichderive from the compounds described by German Patent 1,060,713, andwhich bear additional substituents capable of reaction with isocyanatesand/ or epoxides and which afterwards are brought to reaction withcompounds containing isocyanate or epoxide groups communicating adhesivequalities to the properly adhesive phot-oconductor.

EXAMPLE l8 For the reaction is used a compound not described in GermanPatent 1,060,713, this compound being 1,3-di-m-oxyphenyl-4,S-di-phenyl-imide azole thione (2), fusing point=274C., of following structure:

@ N N'- c C; o

100 g. of the above compound are dissolved in a warm state in 300 cm. ofcyclohexanone, a solution being added to it consisting of 110 g. of anisocyanate component more fully described in Example 8, this compoundhaving approximately 2 isocyanate groups per molecule, dissolved in 200cm. of cyclohexanone, this mixture reacting under reflux boiling atabout 150 C. for 30 minutes.

This solution is then cooled down and left to itself overnight, smallparts of the imide-azole-thione-compound not having reactedcrystallizing out and being filtered off.

100 cm. of the above-mentioned reaction products are added to 75 cm. ofmethyl-ethyl-ketone and to 75 cm. of dioxane. This solution is used forthe production of the electrophotographical layer by spreading it onto apaper the surface of which having been prepared against the intrusion oforganic solvents and afterwards drying this layer.

The eleotrophotographical material thus formed is negatively charged byhelp of a coronar discharge of about 6 kv. and under a positive patternphoto-exposed to a mercury high pressure lamp, and afterwards powderingit with a developing powder in the known way. A positive image of thepattern is obtained which is fixed by heating. The toner used for thedeveloping, with a particle size ranging from 15 to about 50a is mixedwith a support material causing the toner to be charged uptribo-electrically, antipolar to the charge used for the reproduction ofthe image on the paper. Usual toners consist of an artificial resincomponent capable of firmly holding the charge, as, for instance,tolylstyrol, maleinate resins, cumarone resins, phenol resins, productsof resinous qualities from colophonium and others, soots or dyestuffsand eventually with an addition of organic black dyestuffs, as known tobe used for additions to carbonic papers.

EXAMPLE 19 81 g. of 1-m-oxyphenyl-3,4,5-tri-phenyl imide azolone (2),fusing point=190 C., of the fol-lowing structure:

-Q @xyQ After separation and expulsion of the ether a soft resin of highviscosity remains. The reaction product is adequate for the formation ofresilient electrophotographic layers firmly adhering to the support, theaforesaid product undergoing a considerable increase of its hardness andgrinding resistance when burnt in at 130 C.

A solution is added con- 30 cm. of the resinous proper adhesivephotoconductor are dissolved in 100 cm. of cyclohexanone and added to itare 100 cm. of methyl-ethyl-ketone.

This solution is used for the coating of an aluminum plate. Underapplication of measures known for the production of anelectrophotographic image, as hereintofore described, reproductions richin contrasts are obtained.

EXAMPLE 20 The example outlines the use of compounds according to thegeneral formula of German Patent 1,060,714 as the essential ones,containing the component communicating electrophotographic efliciency ifcontaining groupments capable of reaction with epoxides and/orisocyanates and causes them to react toward the production of properlyadhesive photoconductors with isocyanate or epoxide groups containingcompounds.

20 g. of 1,3-di-phenyl-S-p-oxyphenyl-pyrazoline according to Formula 17in German Patent 1,060,714, fusing point=145 C., are dissolved in warmstatus in 60 cm. of cyclohexanone, a solution being added to itconsisting of 58 g. of the modified tri-isocyanate (commercial productproduced and sold by Farbenindustrie Bayer AG. under the trademarkDesmodur L), weight percent in ethyl-acetate and g. of cyclohexanone.After expulsion of the ethylacetate reaction ensues at C. for 10 minutesafter which are added 20 g. of a commonly used C -fat alcohol, andreaction is carried on for a further period of 20 minutes at 115-l20 C.In order to separate the properly adhe- :siv'e photoconductor the abovereaction product is poured into 600 cm. benzine, B.P. 110140 C., Whilestirring the same, the properly adhesive photoconductor beingprecipitated. After washing with benzine the same is dried at 80 C. inan air current.

g. of the dried photoconductor properly adhesive are dissolved in warmstatus in 30 =cm. of cyclohexanone and after cooling down 15 cm.

of methyl-ethyl-ketone are added.

For the production of the electrophotographic layer this solution isspread by centrifuge onto an aluminum plate of high gloss and then driedin an air current at 120 C. An electrophotographic layer of high gloss,firmly adhesive to metals, results having a high degree ofphoto-sensitivity when photo-exposed with UV-fluorescence lamps.

According to the above examples negatively charged with 7 kv. andphoto-exposed under a positive pattern with the application of a directtonerand glass pearls, an electrophotographic contrast image of a highcapacity of photo-dissolution results which can be fixed by heatingand/or the effect of exposure to solvent vapors. Thiselectrophotographic material is excellently suited for the transfer ofthe unfixed electrophotographic image in an electrophotographic fieldonto other materials of plane surface, such as paper, artificial resinfoils or paper-printing patterns commonly used in commerce for theoffset process.

EXAMPLE 21 24 g. of hexane-1,6-diole and 70 g. of a technical mixture of65 weight percent of toluylene-2,4-di-isocyanate and 35 weight percentof toluylene-2,6-di-isocyanate in 250 crn. of cyclohexanone and, causedto react for 4 hours at 145 C.

After distilling off of the cyclohexanone in a vacuum a transparent hardresin is obtained, soluble in cyclohexanone, di-methyl-formamide, higherketones and partly in di-oxane, softening at about 140 C. and melting at210 C. It is suited per se for forming an electrophotographic layer.

For its production 5 g. of the above described reaction product aredissolved in 50 cm. of cyclohexanone.

30 cm. of methyl-ethyl-ketone and 20 cm. of acetone are added.

After the cooling down to This solution is spread by way of a centrifugeonto an aluminum plate chemically or galvanically rendered glossy and ifneed be oxidized, it is then dried at 120 C., a layer thickness of about0003-0008 mm. being formed. The electrophotographic plate is now readyfor use and shows vivid metal gloss being practically colorless. It ismost photo-sensitive in the longer wave-UV- region.

Charged up with 7 kv. under a pattern or by being photo-exposed to longwave UV-light in a photographical process, then developed with a directtoner and glass pearls, an electrophotographic contrast image of strongholding capacity for electrostatic charges results which is caused toadhere by way of usual fixing procedures such as heating or exposing tosolvent vapors.

This electrophotographic material is suited for the production of signboards, patterns and records in the metal industry, for the recording ofpackings, the production of printed current circuits, as well as for thetransfer of the image not yet fixed in an electric field onto othermaterials of plane surfaces.

The following Examples 22, 23 describe the production of properlyadhesive photoconductors the electrophotographically active groupings ofwhich are derived from the class of substituted styryl-phenyl-ketonesand which bear additional substituents capable of reacting with epoxidesand/or isocyanates and have these react for the production of properlyadhesive, preferably resinous, photoconductors with compounds containingepoxide or isocyanate groups said compounds communicating adhesivequalities.

EXAMPLE 22 g. of 4-di-methyl-amino-4-oxy-styryl-phenyl-ketone,

fusing point=205 C., according to the following for- H 0 i colors deepyellow, are dissolved in 300 cm. of cyclohexanone.

88 g. of the modified tri-isocyanate (commercial product produced andsold by Farbenindustrie Bayer AG. under the trademark Desmodur L), 75weight-percent in ethyl-acetate are added and reaction takes place at150 C. for 20 minutes.

cm. of the reacting solution are added to 50 cm. of methyl-ethyl-ketoneand 50 cm. of ethyl-amyl-ketone and after having been spread onto analuminum foil drying takes place at C. in an air current.

Charged up according to the above examples, photoexposed to a mercuryhigh pressure lamp and sufficiently developed, a contrast image, alsofit for transfers, results.

EXAMPLE 23 25 g. of 4-di-methyl-arnino-3-amino-styryl-phenyl-ketone ofthe following structure and of yellow color:

are brought into a solution of 50 g. of an epoxide resin of the type ofdi-phenylpropane reacted with epichlorhydrin, partly under enlargementof molecules condensed per se (commercial product sold under thetrademark Epikote 1001, Shell), brought into 250 cm. ofethyl-amyl-ketone and dissolved under heating and stirring. Held atabout 100 C. for 20 minutes under reflux boiling the solution undergoesa perceivable increase of viscosity.

100 cm. of the reaction product are thinned down with 50 cm. ofmethyl-isobutyl-ketone and 50 cm. of methyl-ethyl-ketone and forproducing a non-adhesive surface added to 5 g. of the modifiedtri-isocyanate (commercial product produced and sold by FarbenindustrieBayer A. G. under the trademark Desmodur L), 75 weight-percent inethyl-acetate, and

0.5 g. of Victoria blue base, according to Schultz, Farbstoiftabellen,1931, vol. 1, No. 822, and at once used for the production of theelectrophotographic layer. For a support material a copper foil is usedhaving an even front side but a sponge conditioned back, and isconnected on its back with a resilient artificial resin of high meltingpoint or with caoutchouc. Onto the front side of this material thedissolved properly adhesive photo-conductor is spread and dried at 100C. in an air current until the expulsion of the solvent has beenachieved and dries it and the front side is heated for a short period at120 C. by radiation heat.

The electrophotographic material is, as described in the above examples,suited for the production of electrophotographic reproductions.

What I claim is:

1. In a photographic reproduction process which comprises exposing anelectrostatically charged, supported photoconductive layer to lightunder a master to discharge the layer at the exposed portions anddeveloping the resulting image with an electroscopic material, theimprovement which comprises employing as the photoconductive layer areaction product of (A) an organic photoconductive compound containinggroups that carry active hydrogens reactive with isocyanates and (B) anorganic compound containing at least two reactive isocyanate groups.

2. The process of claim 1, wherein the organic compound (B) contains theisocyanate groups attached to an aromatic ring system.

3. The process of claim 1, wherein the organic compound (B) is reactedwith a polyhydric alcohol prior to the reaction with the photoconductivecompound (A).

4. The process of claim 1, wherein the organic compound (B) is reactedwith the photoconductive compound (A) and after this reaction furtherreacted with another compound containing groups that react withisocyanates, said other compounds being selected from the groupconsisting of organic compounds containing free hydroxyl groups, monoandpolyamines, and organic compounds containing free carboxyl groups.

5. The process of claim 1, wherein to said reaction product are addedsensitivity dyes to shift the region of spectral sensitizing.

6. The process of claim 1 wherein compound (A) is 2-(4-aminophenyl)-6-methyl benzthiazole, and compound (B) is a tri-isocyanate.

7. The process of claim 1 wherein compound (A) is (4-hydroxybenzylidine)-4'-N-di-ethyl amino-aniline, and compound (B) is atri-isocyanate.

8. The process of claim 1 wherein the photoconductive compound (A) is N4 ethyl (/3 hydroxyethyl)-amino phenyl-methylene-3-nitro-aniline, andcompound (B) is the reaction product of 2-ethyl-2-butyl-propane diol-1,3and toluylene-2,4 (respectively 2,6) diisocyanate.

9. The process of claim 1 wherein the photoconductive compound (A) is4-di-methyl-amino-phenyl-phenyl methylene (3'-hydroXy-aniline) and (B)is a tri-isocyanate.

10. The process of claim 1 wherein the photoconductive compound (A) isN-(4-di-methyl-amino-phenyl)- phenyl methylene 2' methyl4-nitro-5-butyl-aminoaniline, and (B) is a tri-isocyanate.

11. The process of claim 1 wherein the photoconductive compound (A) is N(3 hydroxy napthyl) 4' dimethyl-amino-phenyl-methylene-aniline, and (B)is a triisocyanate.

12. The process of claim 1 wherein the photoconductive compound (A) is2-(4-di-ethyl-amino-2-hydroxy-benzoyl)-benzoic acid, and (B) is areaction product containing three free isocyanate groups per moleculeand produced from one mol of 1-tri-methylol-propane and 3 mols oftoluylene-2,4-di-isocyanate.

13. The process of claim 1 wherein the photoconductive compound (A) is4-amino-4'-di-methyl-amino-benzophenone, and (B) is a tri-isocyanate.

14. The process of claim 1 wherein the photoconductive compound (A) is4-dimethyl-amino-phenyl-3'-hydroxy-napthyl-2-ketone, and (B) is thereaction product of 2-ethyl-2-butyl-propane diol-1,3 andtoluy1ene-2,4-(respectively 2,6) (ii-isocyanate.

15. The process of claim 1 wherein the photoconductive compound (A) is2,7-di-amino-3,6-di-methyl-9-methyl-acridine, and (B) is atri-isocyanate.

16. The process of claim 1 wherein the photoconductive compound (A) is3-amino-6-dimethyl-amino-9-(4-dimethyl-amino-phenyl)-acridine, and (B)is a tri-isocyanate.

17. The process of claim 1 wherein the photoconductive compound (A) is1,3-di-m-hydroxy-phenyl 4,5-diphenyl-imide-azole-thion-(2), and (B) is areaction product containing about 2 isocyanate groups per molecule,being produced from 2-ethyl-2-butyl-propane dio1-1,3 andtoluylene-2,4-(respectively 2,6) (ii-isocyanate.

18. The process of claim 1 wherein the photoconductive compound (A) isl-m-hydroxy phenyl-3,4,5-triphenyl-imide-azolone-(2), and (B) is atri-isocyanate.

19. The process of claim 1 wherein the photoconductive compound (A) is1,3-diphenyl-S-p-hydroxy-phenylpyrazoline and (B) is a tri-isocyanate.

20. The process of claim 1 wherein the photoconductive compound (A) is4-dimethyl-amino-4-hydroxy-styryl-phenyl-ketone, and (B) is atri-isocyanate.

References Cited by the Examiner UNITED STATES PATENTS 2,697,028 12/1954Baker et al. 96-1 2,811,510 10/1957 Leubner et al. 96-1 2,980,535 4/1961Schroeter 96-1 3,025,160 3/1962 Bunge et al. 96-1 3,037,861 6/1962 Hoeglet a1 96-1 3,041,165 6/1962 Sus et al. 96-1 FOREIGN PATENTS 562,3365/1958 Belgium.

NORMAN G. TORCHIN, Primary Examiner.

PHILIP E. MANGAN, Examiner.

1. IN A PHOTOGRAPHIC REPRODUCTION PROCESS WHICH COMPRISES EXPOSING AN ELECTROSTATICALLY CHARGED, SUPPORTED PHOTOCONDUCTIVE LAYER TO LIGHT UNDER A MASTER TO DISCHARGE THE LAYER AT THE EXPOSED PORTIONS AND DEVELOPING THE RESULTING IMAGE WITH AN ELECTROSCOPIC MATERIAL, THE IMPROVEMENT WHICH COMPRISES EMPLOYING AS THE PHOTOCONDUCTIVE LAYER A REACTION PRODUCT OF (A) AN ORGANIC PHOTOCONDUCTIVE COMPOUND CONTAINING GROUPS THAT CARRY ACTIVE HYDROGENS REACTIVE WITH ISOCYANATES AND (B) AN ORGANIC COMPOUND CONTAINING AT LEAST TWO REACTIVE ISOCYANATE GROUPS. 